Deleting Rows in PostgreSQL

So far, we’ve learned how to:

• insert data
• read data
• update data

Now let’s take a look at deleting data from a table.

Deleting rows in PostgreSQL is actually very simple, but it’s also something you need to be very careful with.

Basic DELETE Syntax

The basic syntax for deleting rows looks like this:

delete from table_name
where condition;

• delete from → tells PostgreSQL we want to remove data
• table_name → the table we are deleting from
• where → decides which rows should be deleted

Example: Deleting a Single City

Let’s say we want to delete Tokyo from our cities table.

delete from cities
where name = 'Tokyo';

What PostgreSQL does internally:

1. Looks at all rows in cities 2. Finds rows where name is Tokyo 3. Deletes those rows

In our case, only one row matches, so only that row gets deleted.

Very Important Rule About WHERE

The WHERE clause works exactly the same way as it does in UPDATE.

That means:

• If your WHERE condition matches one row → one row is deleted
• If it matches multiple rows → multiple rows are deleted

Dangerous Example (Be Careful)

Consider this query:

delete from cities
where name != 'Tokyo';